uniq — report or omit repeated lines
Examples (TL;DR)
-
Display each line once:
sort file | uniq -
Display only unique lines:
sort file | uniq -u -
Display only duplicate lines:
sort file | uniq -d -
Display number of occurrences of each line along with that line:
sort file | uniq -c -
Display number of occurrences of each line, sorted by the most frequent:
sort file | uniq -c | sort -nr
Synopsis
uniq [OPTION]... [INPUT [OUTPUT]]
Description
Filter adjacent matching lines from INPUT (or standard input), writing to OUTPUT (or standard output).
With no options, matching lines are merged to the first occurrence.
Mandatory arguments to long options are mandatory for short options too.
- -c, --count
prefix lines by the number of occurrences
- -d, --repeated
only print duplicate lines, one for each group
- -D
print all duplicate lines
- --all-repeated[=METHOD]
like -D, but allow separating groups with an empty line; METHOD={none(default),prepend,separate}
- -f, --skip-fields=N
avoid comparing the first N fields
- --group[=METHOD]
show all items, separating groups with an empty line; METHOD={separate(default),prepend,append,both}
- -i, --ignore-case
ignore differences in case when comparing
- -s, --skip-chars=N
avoid comparing the first N characters
- -u, --unique
only print unique lines
- -z, --zero-terminated
line delimiter is NUL, not newline
- -w, --check-chars=N
compare no more than N characters in lines
- --help
display this help and exit
- --version
output version information and exit
A field is a run of blanks (usually spaces and/or TABs), then non-blank characters. Fields are skipped before chars.
Note: 'uniq' does not detect repeated lines unless they are adjacent. You may want to sort the input first, or use 'sort -u' without 'uniq'. Also, comparisons honor the rules specified by 'LC_COLLATE'.
Reporting Bugs
GNU coreutils online help: <https://www.gnu.org/software/coreutils/>
Report any translation bugs to <https://translationproject.org/team/>
Copyright
Copyright © 2019 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.
See Also
Full documentation <https://www.gnu.org/software/coreutils/uniq>
or available locally via: info '(coreutils) uniq invocation'
Referenced By
bmake(1), comm(1), join(1), sort(1).